ABSTRACT
BACKGROUND/AIMS: This study was undertaken to identify the intracellular signaling pathway involved in induction of macrophage migration inhibitory factor (MIF) in human rheumatoid arthritis (RA) synovial fibroblasts. METHODS: Human RA synovial fibroblasts were treated with concanavalin A (ConA), various cytokines, and inhibitors of signal transduction molecules. The production of MIF by synovial fibroblasts was measured in culture supernatants by ELISA. The expression of MIF mRNA was determined using reverse transcriptase polymerase chain reaction (RT-PCR) and real-time PCR. Phosphorylation of p38 mitogen-activated protein (MAP) kinase in synovial fibroblasts was confirmed using Western blotting. The expression of MIF and p38 MAP kinase in RA synovium was determined using dual immunohistochemistry. RESULTS: The production of MIF by RA synovial fibroblasts increased in a dose-dependent manner after ConA stimulation. MIF was also induced by interferon-gamma, CD40 ligand, interleukin-15, interleukin-1beta, tumor necrosis factor-alpha, and transforming growth factor-beta. The production of MIF by RA synovial fibroblasts was significantly reduced after inhibition of p38 MAP kinase. The expression of MIF and p38 MAP kinase was upregulated in the RA synovium compared with the osteoarthritis synovium. CONCLUSIONS: These results suggest that MIF production was induced through a p38 MAP-kinase-dependent pathway in RA synovial fibroblasts.
Subject(s)
Humans , Arthritis, Rheumatoid/genetics , Base Sequence , Cells, Cultured , Concanavalin A/pharmacology , Cytokines/pharmacology , DNA Primers/genetics , Fibroblasts/drug effects , Macrophage Migration-Inhibitory Factors/biosynthesis , RNA, Messenger/genetics , Signal Transduction/drug effects , Synovial Membrane/drug effects , p38 Mitogen-Activated Protein Kinases/metabolismABSTRACT
The supernatants of peripheral blood lymphocytes of tuberculin-sensitive guinea pigs incubated with PPD were investigated using macrophage and leukocyte migration inhibition tests. Inhibition as well as stimulation of cell migration were observed. The effect upon migration cultures seemed to be dependent upon the immunological state of the host; animals of the V-group (vaccinated once without challenge) showed inhibitory activity to both macrophages and leukocytes, while those in the VC-group (vaccinated and challenged) had stimulatory activity only to leukocytes. The addition of antithymocyte serum stopped all activity (macrophage and leukocyte inhibition and leukocyte stimulation), suggesting that thymus-dependent lymphocytes are necessary for such activity.